Q: A DNA template strand has the sequence 3'-TACGGTACG-5'. What is the corresponding mRNA sequence?

$$5'\text{-}AUGCCAUGC\text{-}3'$$

Question 1

Which of the following best describes the central dogma of molecular biology?

Accepted Answer

DNA \rightarrow RNA \rightarrow Protein

Question 2

During transcription in eukaryotic cells, what is the role of the TATA box?

Accepted Answer

It is a promoter sequence crucial for forming the transcription initiation complex.

Question 3

A mutation changes a codon from UAU (tyrosine) to UAA. What type of mutation is this, and what is its likely effect?

Accepted Answer

Nonsense mutation; introduces a premature stop codon

Question 4

Which of the following statements about prokaryotic and eukaryotic gene expression is correct?

Accepted Answer

In prokaryotes, translation can begin before transcription is finished.

Question 5

A DNA template strand has the sequence 3'-TACGGTACG-5'. What is the corresponding mRNA sequence?

Accepted Answer

$$5'	ext{-}AUGCCAUGC	ext{-}3'$$

Question 6

Which of the following modifications occur to eukaryotic pre-mRNA before it leaves the nucleus?

Accepted Answer

Addition of a 5' cap and a poly-A tail

Question 7

What is the function of aminoacyl-tRNA synthetase in translation?

Accepted Answer

It attaches the correct amino acid to its corresponding tRNA.

Question 8

A mutation causes the insertion of two nucleotides into the coding region of a gene. What is the most likely consequence?

Accepted Answer

A frameshift mutation, likely resulting in a nonfunctional protein

Question 9

Which of the following best explains why the genetic code is described as 'redundant but not ambiguous'?

Accepted Answer

More than one codon can specify the same amino acid, but each codon specifies only one amino acid.

Question 10

A scientist transplants a gene from a jellyfish into a tobacco plant, and the plant glows under UV light. What does this demonstrate about the genetic code?

Accepted Answer

The genetic code is universal among living organisms.

Question 11

During translation, which site on the ribosome holds the tRNA carrying the growing polypeptide chain?

Accepted Answer

P site

Question 12

Which of the following is a function of the 5' cap and poly-A tail added to eukaryotic mRNA?

Accepted Answer

They help protect mRNA from degradation and assist in ribosome binding.

Question 13

A tRNA has the anticodon 3'-UAC-5'. Which mRNA codon will it pair with, and which amino acid will it carry?

Accepted Answer

5'-AUG-3'; Methionine

Question 14

Which of the following best describes alternative RNA splicing?

Accepted Answer

It allows a single gene to code for multiple polypeptides by varying which exons are included.

Question 15

What is the immediate result when a ribosome encounters a stop codon during translation?

Accepted Answer

A release factor binds, causing the addition of a water molecule and release of the polypeptide.

Question 16

Which of the following is a post-translational modification that can affect protein function?

Accepted Answer

Glycosylation (addition of a sugar group)

Question 17

A patient has a genetic disorder caused by a single nucleotide substitution that changes a codon from GAG to GTG in the β-globin gene. What is the effect at the protein level?

Accepted Answer

The amino acid glutamic acid is replaced by valine, causing sickle-cell hemoglobin.

Question 18

Which of the following best explains why frameshift mutations are often more severe than point mutations?

Accepted Answer

They can alter the entire reading frame, changing every amino acid downstream.

Question 19

In eukaryotic cells, what is the fate of introns after RNA splicing?

Accepted Answer

They are removed and degraded.

Question 20

Which of the following best describes the function of a signal peptide during protein synthesis?

Accepted Answer

It directs the ribosome to the endoplasmic reticulum for protein targeting.

Gene Expression: Transcription, Translation, and Mutations

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